The sprue is the extension of the injection nozzle into the mold.
In a single cavity mold with a single injection location, the sprue can meet at the cavity wall. The sprue is usually connected to a runner system as shown in the following diagram.
The angle of the taper on a sprue should be large enough for it to be easily ejected, but not too large because the cooling time and the required amount of material increases along with the size of the sprue diameter.